The most common glass composition for making continuous glass fiber strands is “E-Glass.” The liquidus temperature of E-Glass is approximately 2100° F. (1149° C.) or lower. One advantage of E-Glass is that its liquidus temperature allows operating temperatures for producing glass fibers to be approximately 1900° F. to 2400° F. (1038° C. to 1316° C.). The ASTM classification for E-glass fiber yarns used in printed circuit boards and aerospace applications defines the composition to be 52 to 56 weight % SiO2, 16 to 25 weight % CaO, 12 to 16 weight % Al2O3, 5 to 10 weight % B2O3, 0 to 5 weight % MgO, 0 to 2 weight % Na2O and K2O, 0 to 0.8 weight % TiO2, 0.05 to 0.4 weight % Fe2O3 and 0 to 1.0 weight % Fluorine.
Boron-free fibers are sold under the trademark ADVANTEX (Owens Corning, Toledo, Ohio, USA). Boron-Free fibers, such as are disclosed in U.S. Pat. No. 5,789,329, incorporated herein by reference in its entirety, offer a significant improvement in operating temperatures over boron-containing E-glass. Boron-Free glass fibers fall under the ASTM definition for E-glass fibers for use in general-use applications.
S-Glass is a family of glasses composed primarily of the oxides of magnesium, aluminum, and silicon with a chemical composition that produces glass fibers having a higher mechanical strength than E-Glass fibers. The composition for forming S-Glass includes approximately 65 weight % SiO2, 25 weight % Al2O3, and 10 weight % MgO. S-glass has a composition that was originally designed to be used in high-strength applications such as ballistic armor.
R-Glass is a family of glasses that are composed primarily of the oxides of silicon, aluminum, magnesium, and calcium with a chemical composition that produces glass fibers with a higher mechanical strength than E-Glass fibers. R-Glass has a composition that contains approximately 58-60 weight % SiO2, 23.5-25.5 weight % Al2O3, 14-17 weight % CaO plus MgO, 0% B2O3, 0% F2 and less than 2 weight % miscellaneous components. R-Glass contains more alumina and silica than E-Glass and requires higher melting and processing temperatures during fiber forming. Typically, the melting and processing temperatures for R-Glass are at least 160° C. higher than those for E-Glass. This increase in processing temperature requires the use of a high-cost platinum-lined melter. In addition, the close proximity of the liquidus temperature to the forming temperature in R-Glass requires that the glass be fiberized at a viscosity lower than E-Glass, which is customarily fiberized at or near 1000 poise. Fiberizing R-Glass at the customary 1000 poise viscosity would likely result in glass devitrification, which causes process interruptions and reduced productivity.
Tables IA-IE set forth the compositions for a number of conventional high-strength glass compositions.
TABLE I-AChineseRUSSIANHighCONTINUOUSNITTOBO “T”StrengthROVING MAGNESIUMNITTOBO “T”Glass FabricConstituentglassALUMINOSILICATEGlass Fabric “B”(Yarn) “C”SiO255.0855.8164.5864.64CaO0.330.380.440.40Al2O325.2223.7824.4424.57B2O31.850.030.03MgO15.9615.089.959.92Na2O0.120.0630.080.09Fluorine0.030.0340.037TiO20.0232.330.0190.018Fe2O31.10.3880.1870.180K2O0.0390.560.0070.010ZrO20.0070.15Cr2O30.0110.0030.003Li2O1.63CeO2
TABLE I-BNittoNittoVetrotex SaintBosekiBosekiNitto Boseki TEGobain SR GlassPolotskA&PNT6030Glass RST-Stratifils SR CGSTEKLOVOLOKNOConstituentYarnYarn220PA-535CS250 P109High Strength GlassSiO265.5164.6064.2063.9058.64CaO0.440.580.630.260.61Al2O324.0624.6025.1024.4025.41B2O30.04MgO9.739.909.9010.0014.18Na2O0.040.060.0200.0390.05Fluorine0.070.02TiO20.0160.0000.0000.2100.624Fe2O30.0670.0790.0830.5200.253K2O0.0200.0200.0200.5400.35ZrO20.079Cr2O30.00100.0010.023Li2OCeO2
TABLE I-CChineseHighChinese HighStrengthStrength YarnGlassZentron S-2SOLAIS GlassAdvanced GlassConstituent(8 micron)RovingGlass RovingSampleYarns R GlassSiO255.2255.4964.7464.8158.46CaO0.730.290.140.559.39Al2O324.4224.8824.7024.5124.55B2O33.463.520.020.04MgO12.4612.2810.249.355.91Na2O0.1040.060.170.160.079Fluorine0.070.020.054TiO20.320.360.0150.040.196Fe2O30.9800.9300.0450.2380.400K2O0.2400.1500.0050.030.67ZrO2Cr2O30.00500.0070.005Li2O0.590.63CeO21.231.25
TABLE I-DAdvancedIVG VertexGlass YarnsCulimetaIVG Vertex B96IVG VertexOutside #1 GlassConstituentS GlassRoving675 YarnGlass RovingRovingSiO264.6159.3758.3458.5858.12CaO0.170.270.310.300.31Al2O324.8425.4923.8124.2624.09B2O30.040.05MgO10.1113.4714.9915.0215.36Na2O0.1180.0240.050.020.03Fluorine0.030.040.040.04TiO20.0110.5301.3800.670.91Fe2O30.0420.3740.3330.3360.303K2O0.480.420.280.29ZrO20.1520.1290.1650.157Cr2O30.00500.01200.01000.01200.0120Li2OCeO2
TABLE I-EIVG VertexRH CG250Outside #2P109 GlassConstituentGlass RovingFiber StrandSiO258.6958.54CaO0.299.35Al2O324.325.39B2O3MgO15.066.15Na2O0.030.10Fluorine0.040.16TiO20.640.008Fe2O30.3310.069K2O0.360.14ZrO20.1870.006Cr2O30.0130Li2OCeO2
R-Glass and S-Glass are produced by melting the constituents of the compositions in a platinum-lined melting container. The costs of forming R-Glass and S-Glass fibers are dramatically higher than E-Glass fibers due to the cost of producing the fibers in such melters. Thus, there is a need in the art for methods of forming glass compositions useful in the formation of high performance glass fibers from a direct-melt process in a refractory-lined furnace and fibers formed by the method.